BOJ 14786 - Ax+Bsin(x)=C ② [C]

문제

링크

풀이

#include <stdio.h>
#include <math.h>
 
long double ab(long double x) {
  return x < 0 ? -x : x;
}
 
long double newton(long double a, long double b, long double c, long double x) {
  return x - (a*x+b*sin(x)-c) / (a+b*cos(x));
}
 
int main(void) {
  int a, b, c;
 
  scanf("%d %d %d", &a, &b, &c);
 
  long double x = (long double)c/a;
  long double x_pre = x-1;
  while (ab(x-x_pre) > 1e-10) {
    x_pre = x;
    x = newton((long double)a, (long double)b, (long double)c, x);
  }
 
  printf("%.20Lf", x);
  return 0;
}